Enter a route number to display the stops (and switch between alternate routes in the sidebar). A click on a marker or a stop name will show a blow-up map for that location (which can be maximised to show a StreetView of that location, or at least it would if StreetView was available in London). A selection of Wikipedia items near that stop will also be displayed, so you can use this to explore locations along the route; again, these maximise to show the whole Wikipedia page inline.